Check valves of various designs are employed in many industries with plants having the fluid handling systems. Among many different check valves, the ball check valve with a spring biased ball or with a free floating ball is the most popular, for it is more reliable, compact, and economic compared with other types of check valves. However, these highly popular ball check valves have a number of short-comings. The ball check valve is not a straight-through flow type check valve because the ball is always in the way of the flow passage. Since the ball is in the middle of the fluid stream, the surface of the ball wears rapidly when the fluid stream is of an abrasive nature and, consequently, it causes a leak in checking the back flow. The ball check valve is not a slow-acting check valve because the ball slams back to the checking seat when there is a reverse pressure gradient of a large magnitude. The ball check valve is a truly ideal check valve only if it has a straight-through flow passage and is capable of withstanding a reverse pressure gradient of a large magnitude.
The primary object of the present invention is to provide the ball-plug pendulum check valve with the straight-through flow passage while it checks the reverse flow in the bubble-tight manner like a conventional ball check valve.
Another object of the present invention is to provide the ball-plug pendulum check valve with a large bearing surface for the ball-plug, which bearing surface is separated from the seating surface.
A further object of the present invention is to provide the ball-plug pendulum check valve with slowly acting capability under a sudden reverse pressure gradient, which operates smoothly under a large reverse pressure surge without creating water hammering.
Still another object of the present invention is to provide the ball-plug pendulum check valve wherein the seating surface and the seal arrangement for checking the reverse flow is protected from the abrasive action of the flow.
Still a further object of the present invention is to provide a check valve applicable to fluid handling at an extremely high pressure.
These and other objects of the present invention will become clear as the description thereof proceeds.